1. Field of the Invention
The present invention generally relates to servo circuits for controlling an optical pickup of a reproducing apparatus such as an optical disc reproducing apparatus or the like and, more particularly, to a servo circuit having a bi-axial actuator supported by a plurality of wires or the like which can carry out a tracking servo of an optical pickup having a high natural frequency (fo) and Q-value (Q).
2. Description of the Related Art
When a tracking servo is effected in the optical disc reproducing apparatus, for example, a tracking error signal is supplied to a phase compensator circuit to increase the level of low band of the error signal. Then, the error signal thus phase-compensated is supplied to a drive amplifier and a drive signal from this drive amplifier is supplied to a tracking coil of an optical pickup. However, in the apparatus using such phase compensator circuit, as the gain of the low band of the error signal is increased, a phase delay tends to occur in the low band component. In particular, when the tracking servo is effected on an actuator in which a drive magnet, an objective lens or the like are unitarily supported by wire members, the natural frequency fo and the Q value thereof become higher than those of an actuator supported by means of a mold hinge. There is then the risk that the actuator is oscillated.